Woopsi offers a GUI library for Nintendo. The Open Source Library offers help in quickly creating user interfaces for homebrew software. The Woopsi is based on the AmigaOS windowing system.
The first package which includes full source code and files of Woopsi library is now available on SourceForge.
There are two packages - the Demo package contains pre-built binaries for the NDS that can be used in either a DS emulator or with a flash cart and a real DS. It is a tech demo of Woopsi's functionality.
The second package contains the full source code of the demo and the source code for Woopsi.
Source:
https://sourceforge.net/projects/woopsi